An 'Extremely Rare' Half-Male, Half-Female Bird Temporarily Took Up Residence Outside of Chicago
The unusual-looking bobolink is what's called a bilateral gynandromorph. The bird behaved like a male, eventually wooing a mate and raising fledglings
An exceptionally rare bobolink with both male and female characteristics took up residence near Chicago, delighting birdwatchers who got a rare chance to observe this biological phenomenon. The bobolink, dubbed "Black and Tan," is a bilateral gynandromorph, with its right side being male and its left side female. This rare condition occurs due to a genetic anomaly during the development of the bird's egg cell, resulting in two distinct sets of chromosomes.
Ornithologists confirmed Black and Tan's status, and despite its unique appearance, the bird exhibited typical male bobolink behavior, including singing, performing courtship flights, and establishing a breeding territory. Remarkably, Black and Tan also successfully nested, reproduced, and raised fledglings. The bird has since left the area, but conservationists hope it will return next spring.
Gynandromorphism is extremely rare, occurring in fewer than 100 individual birds among the world's 11,000 bird species. While the exact causes remain unclear, researchers believe it likely emerges from a genetic error during female meiosis, resulting in an egg cell with both male and female chromosomes.
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